Williamsport is a place name in Onekama Township, Manistee County in the U.S. state of Michigan.

The place takes its name from the steam tug Williams, which was the first vessel to enter the man-made cut on 15 May 1871.

William Shanks and his wife Annie operated a boarding house and picnic grounds at the site of Williamsport and platted their homestead land as a village.

A saw mill was built at the site, but it burned shortly after construction and was never rebuilt.

The move of the village from Portage Point to the present location of Onekama at the northeastern end of the lake quashed the Shankses' plans for the development of Williamsport.